Effect of oxygen-staging on fluidized preheating combustion of pulverized coal under O2/CO2 atmosphere

Oxy-fuel combustion with low NOx emission has been received more attention in recent years. In this work, a series of oxygen-staged experimental investigations of Shenmu bituminous coal with the preheated combustion technology was carried out under O2/CO2 atmosphere to obtain the effect of oxygen-staged on combustion and NOx emission. The results showed that the increase of excess oxygen coefficient of the primary air(lambda Pr) decreased the temperature difference at each measuring point in the circulating fluidized bed, promoted the production of coal gas, facilitated the release of elements, and improved the mass conversion ratio of volatile matter up to 92.3%. Besides, the increase of lambda Pr inhibited the conversion process of N-5 to N-6. At the same time, the release of nitrogen-containing volatile matter during the partial gasification process was also reduced. As the lambda Pr increases, reducing the excess oxygen coefficient of the secondary air(lambda Se) or increasing the oxygen partial pressure of primary air were beneficial to reduce the emissions of NOx to a certain extent.